Aneural tissue culture of human muscle has recently contributed to elucidating the pathogenesis of several neuromuscular diseases. In a number of those diseases, the morphologic and/or biochemical defects were reproduced in aneural culture, indicating abnormalities intrinsic to the muscle cell. Nevertheless, there are still human neuromuscular diseases in which a defect has not been evident in cultured muscle. Possibly in regard to some neuromuscular diseases, cultured muscle should be innervated and in a more advanced state of development in order for a defect to become manifest in tissue culture. The objectives of this project are to study innervated adult human muscle in tissue culture and to achieve more advanced maturation of the cultured human muscle, by co-culture with motor neurons or exposure to neural extracts, so it will have many of the properties exhibited by adult human muscle in vivo. Detailed histochemical, electronmicroscopic, ultrastructural-cytochemical, and biochemical studies will help delineate the effects of innervation of cultured normal and diseased human muscle. The ultimate goal is to utilize the innervated cultures to detail the pathogeneses of human neuromuscular diseases. Once disease-characteristic abnormalities are demonstrated in culture, attempts will be made to define the pathogenesis. And, we will attempt to correct, i.e., treat, the defect in culture, which could be an approach useful for preclinical screening of treatments for patients.